The invention relates to compositions containing at least one (co)polycarbonate stable at high temperature and at least one ethylene-alkyl acrylate block copolymer. This application furthermore relates to mouldings or injection moulded parts and extrudates obtainable from these compositions, and to processes for the preparation of the polycarbonate compositions, and to the mouldings and extrudates. These polycarbonate compositions are distinguished in that, together with high thermal stability, the flexural fatigue strength of the films produced from the resulting material is improved.
In automobile seats, films via which the triggering of the airbag is controlled are used: depending on the weight of the person and the seat position, the airbag is selectively triggered. These films must be stable to high temperatures so that, in printing with electrically conductive paste, it is possible to use drying temperatures which are as high as possible. Owing to the bending stress in the seat surface, the film must additionally meet particular requirements regarding the flexing resistance (flexural fatigue strength, determinable via the double fold number according to Schopper according to ISO 5625).
The uses of polycarbonate stable at high temperature as a base material of films is known. These products, inter alia obtainable as Bayfol® 1202 from Bayer MaterialScience AG, are used, for example, in loudspeaker membranes.
These films are very suitable for the application described above, owing to their high thermal stability, but the flexing resistance of the products is insufficient.
An improvement in the mechanical properties of polymers by addition of elastomers is known per se.
For example, WO 2006/01570 A1 describes the mixtures of polycarbonates and 0.1-50% by weight of the ethylene-alkyl acrylate copolymers. The material thus obtained has a high impact strength in combination with high flowability while retaining the other properties. However, this document does not disclose polycarbonates stable at high temperature, which are important for the desired applications. There is no indication of improvement of the double fold numbers in this laid-open application.
WO 2005/042638 A1 describes the improvement of polycarbonate/ABS blends by the addition of modifiers in the compulsory combination of ethylene-alkyl acrylate copolymer with ethylene/butyl acrylate/glycidyl methacrylate terpolymer. Here too, this document does not disclose polycarbonates stable at high temperature in the composition according to the invention.
EP 362 646 A2 describes compositions of polycarbonates having high heat distortion resistance with elastomers. Improved properties with regard to double fold numbers on the other hand are not described. However, this laid-open application gives no indication that the special modifier in the application according to the invention leads to the desired aim.
DE 40 09 759 A1 describes the mixture of polypropylene with polycarbonates having high heat distortion resistance as a method for producing mixtures having better compatibility.
EP 722 984 A2 describes mixtures of polycarbonate stable at high temperature and terpolymers of ethylene, acrylates and epoxy-functionalized monomers. The effect here is an increase in the stress cracking resistance and impact strength of the polycarbonate while the heat distortion resistance is retained. However, the present application relates to compositions of different nature.
In the context of this application, polycarbonate compositions (or blends) are understood as meaning mixtures of two or more polycarbonates which may optionally be provided with additives.
Starting from the prior art, it was thus the object to develop compositions of polycarbonates which have high heat distortion resistance, said compositions having an improved flexural fatigue strength.